Vibration dampers with such sensor devices are used with damping regulators, and particularly, in so-called vehicle movement dynamic systems, where use is made of the most varied sensor principles for the position determination.
Thus, for example, EP 0 509 244 A1 discloses such a sensor device, in which a cylindrical spool, rigidly connected to the damping piston, forms--with the damping cylinder, which is made of magnetizable material--an inductive resistor, which is dependent on their relative position to one another. The evaluation of this resistance gives a measure of the position of the damping piston in the damping cylinder. The electronic control and evaluation circuit of this sensor device is hereby located away from the vibration damper and thus from the sensor element, which brings about an increased susceptibility of the arrangement with respect to external influences. This becomes particularly significant if in order to attain a higher resolution and accuracy of the position signal, the sensitivity of the sensor device is increased or sensor principles which are, per se, more sensitive, are used.
Furthermore, DE 33 12 881 C2 made known a sensor device for the measurement of the position of a damping piston in a damping cylinder of a vibration damper for motor vehicles, in which a sensor element and a control and evaluation circuit is located in the hollow piston rod, which is closed off by a lid. However, whether the measurement signal produced by the sensor device is transmitted to a control device located outside the vibration damper and, if so, how this is done is not disclosed in this publication.
Proceeding from this state of the art, the goal of the invention therefore is to create a sensor device of the initially mentioned type, in which, in particular, the problem of sealing the electronic circuit, with respect to the harsh environmental conditions of the corresponding building space, which is concomitant with placing the pertinent electronic control and evaluation circuit in the immediate vicinity of the sensor element--that is, within the vibration damper, is solved.
The goal of the invention is attained by a sensor device, in which the sensor element and the electronic control and evaluation circuit are located in a housing and are hermetically enclosed, with respect to the outside, by a surrounding seal which lies between the piston rod and the cover of the damping piston, where the connecting cable provided for the electrical connection of the sensor device with a control device located at a distance is conducted through this surrounding seal in a connecting area provided therefore.
Advantageous refinements of the object of the invention can be deduced from the subordinate claims and from the subsequent description of the embodiment examples shown in the drawings.